Actual source code: lcd.c

petsc-3.7.3 2016-07-24
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  2: #include <../src/ksp/ksp/impls/lcd/lcdimpl.h>

  6: PetscErrorCode KSPSetUp_LCD(KSP ksp)
  7: {
  8:   KSP_LCD        *lcd = (KSP_LCD*)ksp->data;
 10:   PetscInt       restart = lcd->restart;

 13:   /* get work vectors needed by LCD */
 14:   KSPSetWorkVecs(ksp,2);

 16:   VecDuplicateVecs(ksp->work[0],restart+1,&lcd->P);
 17:   VecDuplicateVecs(ksp->work[0], restart + 1, &lcd->Q);
 18:   PetscLogObjectMemory((PetscObject)ksp,2*(restart+2)*sizeof(Vec));
 19:   return(0);
 20: }

 22: /*     KSPSolve_LCD - This routine actually applies the left conjugate
 23:     direction method

 25:    Input Parameter:
 26: .     ksp - the Krylov space object that was set to use LCD, by, for
 27:             example, KSPCreate(MPI_Comm,KSP *ksp); KSPSetType(ksp,KSPLCD);

 29:    Output Parameter:
 30: .     its - number of iterations used

 32: */
 35: PetscErrorCode  KSPSolve_LCD(KSP ksp)
 36: {
 38:   PetscInt       it,j,max_k;
 39:   PetscScalar    alfa, beta, num, den, mone;
 40:   PetscReal      rnorm;
 41:   Vec            X,B,R,Z;
 42:   KSP_LCD        *lcd;
 43:   Mat            Amat,Pmat;
 44:   PetscBool      diagonalscale;

 47:   PCGetDiagonalScale(ksp->pc,&diagonalscale);
 48:   if (diagonalscale) SETERRQ1(PetscObjectComm((PetscObject)ksp),PETSC_ERR_SUP,"Krylov method %s does not support diagonal scaling",((PetscObject)ksp)->type_name);

 50:   lcd   = (KSP_LCD*)ksp->data;
 51:   X     = ksp->vec_sol;
 52:   B     = ksp->vec_rhs;
 53:   R     = ksp->work[0];
 54:   Z     = ksp->work[1];
 55:   max_k = lcd->restart;
 56:   mone  = -1;

 58:   PCGetOperators(ksp->pc,&Amat,&Pmat);

 60:   ksp->its = 0;
 61:   if (!ksp->guess_zero) {
 62:     KSP_MatMult(ksp,Amat,X,Z);             /*   z <- b - Ax       */
 63:     VecAYPX(Z,mone,B);
 64:   } else {
 65:     VecCopy(B,Z);                         /*     z <- b (x is 0) */
 66:   }

 68:   KSP_PCApply(ksp,Z,R);                   /*     r <- M^-1z         */
 69:   VecNorm(R,NORM_2,&rnorm);
 70:   KSPLogResidualHistory(ksp,rnorm);
 71:   KSPMonitor(ksp,0,rnorm);
 72:   ksp->rnorm = rnorm;

 74:   /* test for convergence */
 75:   (*ksp->converged)(ksp,0,rnorm,&ksp->reason,ksp->cnvP);
 76:   if (ksp->reason) return(0);

 78:   VecCopy(R,lcd->P[0]);

 80:   while (!ksp->reason && ksp->its < ksp->max_it) {
 81:     it   = 0;
 82:     KSP_MatMult(ksp,Amat,lcd->P[it],Z);
 83:     KSP_PCApply(ksp,Z,lcd->Q[it]);

 85:     while (!ksp->reason && it < max_k && ksp->its < ksp->max_it) {
 86:       ksp->its++;
 87:       VecDot(lcd->P[it],R,&num);
 88:       VecDot(lcd->P[it],lcd->Q[it], &den);
 89:       alfa = num/den;
 90:       VecAXPY(X,alfa,lcd->P[it]);
 91:       VecAXPY(R,-alfa,lcd->Q[it]);
 92:       VecNorm(R,NORM_2,&rnorm);

 94:       ksp->rnorm = rnorm;
 95:       KSPLogResidualHistory(ksp,rnorm);
 96:       KSPMonitor(ksp,ksp->its,rnorm);
 97:       (*ksp->converged)(ksp,ksp->its,rnorm,&ksp->reason,ksp->cnvP);

 99:       if (ksp->reason) break;

101:       VecCopy(R,lcd->P[it+1]);
102:       KSP_MatMult(ksp,Amat,lcd->P[it+1],Z);
103:       KSP_PCApply(ksp,Z,lcd->Q[it+1]);

105:       for (j = 0; j <= it; j++) {
106:         VecDot(lcd->P[j],lcd->Q[it+1],&num);
107:         VecDot(lcd->P[j],lcd->Q[j],&den);
108:         beta = -num/den;
109:         VecAXPY(lcd->P[it+1],beta,lcd->P[j]);
110:         VecAXPY(lcd->Q[it+1],beta,lcd->Q[j]);
111:       }
112:       it++;
113:     }
114:     VecCopy(lcd->P[it],lcd->P[0]);
115:   }
116:   if (ksp->its >= ksp->max_it && !ksp->reason) ksp->reason = KSP_DIVERGED_ITS;
117:   VecCopy(X,ksp->vec_sol);
118:   return(0);
119: }
120: /*
121:        KSPDestroy_LCD - Frees all memory space used by the Krylov method

123: */
126: PetscErrorCode KSPReset_LCD(KSP ksp)
127: {
128:   KSP_LCD        *lcd = (KSP_LCD*)ksp->data;

132:   if (lcd->P) { VecDestroyVecs(lcd->restart+1,&lcd->P);}
133:   if (lcd->Q) { VecDestroyVecs(lcd->restart+1,&lcd->Q);}
134:   return(0);
135: }


140: PetscErrorCode KSPDestroy_LCD(KSP ksp)
141: {

145:   KSPReset_LCD(ksp);
146:   PetscFree(ksp->data);
147:   return(0);
148: }

150: /*
151:      KSPView_LCD - Prints information about the current Krylov method being used

153:       Currently this only prints information to a file (or stdout) about the
154:       symmetry of the problem. If your Krylov method has special options or
155:       flags that information should be printed here.

157: */
160: PetscErrorCode KSPView_LCD(KSP ksp,PetscViewer viewer)
161: {

163:   KSP_LCD        *lcd = (KSP_LCD*)ksp->data;
165:   PetscBool      iascii;

168:   PetscObjectTypeCompare((PetscObject)viewer,PETSCVIEWERASCII,&iascii);
169:   if (iascii) {
170:     PetscViewerASCIIPrintf(viewer,"  LCD: restart=%d\n",lcd->restart);
171:     PetscViewerASCIIPrintf(viewer,"  LCD: happy breakdown tolerance %g\n",lcd->haptol);
172:   }
173:   return(0);
174: }

176: /*
177:     KSPSetFromOptions_LCD - Checks the options database for options related to the
178:                             LCD method.
179: */
182: PetscErrorCode KSPSetFromOptions_LCD(PetscOptionItems *PetscOptionsObject,KSP ksp)
183: {
185:   PetscBool      flg;
186:   KSP_LCD        *lcd = (KSP_LCD*)ksp->data;

189:   PetscOptionsHead(PetscOptionsObject,"KSP LCD options");
190:   PetscOptionsInt("-ksp_lcd_restart","Number of vectors conjugate","KSPLCDSetRestart",lcd->restart,&lcd->restart,&flg);
191:   if (flg && lcd->restart < 1) SETERRQ(PetscObjectComm((PetscObject)ksp),PETSC_ERR_ARG_OUTOFRANGE,"Restart must be positive");
192:   PetscOptionsReal("-ksp_lcd_haptol","Tolerance for exact convergence (happy ending)","KSPLCDSetHapTol",lcd->haptol,&lcd->haptol,&flg);
193:   if (flg && lcd->haptol < 0.0) SETERRQ(PetscObjectComm((PetscObject)ksp),PETSC_ERR_ARG_OUTOFRANGE,"Tolerance must be non-negative");
194:   return(0);
195: }

197: /*MC
198:      KSPLCD -  Implements the LCD (left conjugate direction) method in PETSc.

200:    Options Database Keys:
201: +   -ksp_lcd_restart - number of vectors conjudate
202: -   -ksp_lcd_haptol - tolerance for exact convergence (happing ending)

204:    Level: beginner

206:     Notes: Support only for left preconditioning

208:     References:
209: +    1. - J.Y. Yuan, G.H.Golub, R.J. Plemmons, and W.A.G. Cecilio. Semiconjugate
210:      direction methods for real positive definite system. BIT Numerical
211:      Mathematics, 44(1),2004.
212: .    2. - Y. Dai and J.Y. Yuan. Study on semiconjugate direction methods for
213:      nonsymmetric systems. International Journal for Numerical Methods in
214:      Engineering, 60, 2004.
215: .    3. - L. Catabriga, A.L.G.A. Coutinho, and L.P.Franca. Evaluating the LCD
216:      algorithm for solving linear systems of equations arising from implicit
217:      SUPG formulation of compressible flows. International Journal for
218:      Numerical Methods in Engineering, 60, 2004
219: -    4. - L. Catabriga, A. M. P. Valli, B. Z. Melotti, L. M. Pessoa,
220:      A. L. G. A. Coutinho, Performance of LCD iterative method in the finite
221:      element and finite difference solution of convection diffusion
222:      equations,  Communications in Numerical Methods in Engineering, (Early
223:      View).

225:   Contributed by: Lucia Catabriga <luciac@ices.utexas.edu>


228: .seealso:  KSPCreate(), KSPSetType(), KSPType (for list of available types), KSP,
229:            KSPCGSetType(), KSPLCDSetRestart(), KSPLCDSetHapTol()

231: M*/

235: PETSC_EXTERN PetscErrorCode KSPCreate_LCD(KSP ksp)
236: {
238:   KSP_LCD        *lcd;

241:   PetscNewLog(ksp,&lcd);
242:   ksp->data    = (void*)lcd;
243:   KSPSetSupportedNorm(ksp,KSP_NORM_PRECONDITIONED,PC_LEFT,3);
244:   lcd->restart = 30;
245:   lcd->haptol  = 1.0e-30;

247:   /*
248:        Sets the functions that are associated with this data structure
249:        (in C++ this is the same as defining virtual functions)
250:   */
251:   ksp->ops->setup          = KSPSetUp_LCD;
252:   ksp->ops->solve          = KSPSolve_LCD;
253:   ksp->ops->reset          = KSPReset_LCD;
254:   ksp->ops->destroy        = KSPDestroy_LCD;
255:   ksp->ops->view           = KSPView_LCD;
256:   ksp->ops->setfromoptions = KSPSetFromOptions_LCD;
257:   ksp->ops->buildsolution  = KSPBuildSolutionDefault;
258:   ksp->ops->buildresidual  = KSPBuildResidualDefault;
259:   return(0);
260: }